Defendant, who was 84-year-old victim's live-in caregiver, was convicted, after bench trial, of first degree murder and aggravated battery of a senior citizen. Defendant filed postconviction petition alleging that trial counsel was ineffective in failing to conduct a diligent investigation to discover that intervening gross negligence of treating medical staff, rather than Defendant's conduct in slapping and putting his forearm against throat, caused death, Had counsel investigated defense of intervening cause, he would have discovered expert witness and thus viable defense; thus, Defendant made substantial showing that counsel rendered deficient performance. (KILBRIDE, FREEMAN, THOMAS, GARMAN, and KARMEIER, concurring.)